When running Lagrangian Particle Tracking, either with the solver icoUncoupledKinematicParcelFoam or the icoUncoupledKinematicCloud function object with the pimpleFoam solver, I observe strange behaviour by the Lagrangian Particles.

The header-description of the cellPointWallModified interpolation scheme states:

Same as interpolationCellPoint, but if interpolating a wall face, uses cell centre value instead

Thus, one would expect that particles in a cell next to the wall will move with the cell velocity. However, this is not the case.

Steps To Reproduce

I attached a 2D lid-driven cavity case for use with icoUncoupledKinematicParcelFoam, and a 3D lid-driven cavity case for use with pimpleFoam.
The archive also contains some screenshots of the solution of the these cases.

The cavity cases are set up to use the sphereDrag force as the only force acting on the particles. Thus, we expect the particles to follow the flow. However, the particles tend to stick to the wall (in OF-5.x) or be caught up in the first internal face parallel, and next to the wall (OF-4.1).

Additional Information

With the cavity case in OF-5.x, the only interpolation schemes that leave the particles to freely move around are cell, and cellPatchConstrained.

All other interpolation schemes result in particles getting stuck on the wall. This is not surprising for schemes such as cellPoint, however, unexpected for the cellPointWallModified scheme.

A new version of this interpolation scheme has now been developed, as a result of maintenance funding. The new implementation modifies extrapolated wall velocities so that they do not point out of the domain. This should provide a "slippy" boundary as with the previous implementation, but without the potential for incompatibility with rebound wall interactions. This implementation has been pushed to dev as commit 63b641a0.